How does a search engine decide which pages to show you when you search?

When a user enters a search query into a search engine, all the pages that are considered relevant are identified in the index and an algorithm is used to hierarchically rank the relevant pages in a result set. The algorithms used to rank the most relevant results vary for each search engine. As we mentioned in chapter 1, search engines are automatic response machines. They exist to discover, understand and organize Internet content in order to provide the most relevant results to the questions asked by search engines.

So for search users, it's simple. They enter their query and search engines review their index of web pages to find the best matches. Those matches are then ranked using an algorithm and displayed on search engine results pages (SERPs). They can answer questions directly on search engine results pages, display different types of content, and even change the SERPs to reflect the queries.

Let's take a look at the general procedures on which each search engine algorithm is based, and then look at the four main platforms to see how they do it. Many sites make the serious mistake of structuring their navigation in a way that is inaccessible to search engines, which hinders their ability to appear in search results. For example, you can search for “shoes” on Amazon and then refine your search by size, color, and style. A search engine like Google has its own index of local business listings, from which it creates local search results.

Once pages are crawled and indexed, they are eligible to be displayed on a search engine results page (SERP). If you have a page that you want search engines to find, but to which there are no links from any other page, it's practically invisible. Having this basic knowledge can help you solve crawling problems, index your pages and learn how to optimize the way your site appears in Google Search. To determine relevance, search engines use algorithms, a process or formula by which stored information is retrieved and ordered in a meaningful way.

Since Google needs to maintain and improve the quality of searches, it seems inevitable that interaction metrics are more than just a correlation, but it seems that Google fails to qualify engagement metrics as a “ranking signal”, since those metrics are used to improve the quality of the search, and the range of individual URLs is just a by-product of that. The x-robots tag is used in the HTTP header of the URL, which provides more flexibility and functionality than meta tags if you want to block search engines on a large scale, since you can use regular expressions, block non-HTML files and apply noindex tags throughout the site. If search engines are response machines, content is the means by which search engines provide those answers. Its search engine is effectively governed by rules similar to those of Google, the owner of the platform, and focuses on keywords and relevance.

There is no single place where all websites and pages are located, so search engines must constantly search for new pages and add them to their index.